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<H1><A NAME=SECTION00020000000000000000> Introduction</A></H1>
<P>
<H6><A NAME=SectionIntro>&#160;</A></H6>
<P>
<tt> LASPack</tt>
  is a package for solving large sparse systems of linear equations
like those which arise from the discretization of partial differential 
equations.
<P>
<P>
<P>
Main features:
<UL><LI> 
  The primary aim of <tt> LASPack</tt>
  is the implementation of efficient iterative
  methods for the solution of systems of linear equations.
  All routines and data structures are optimized for effective usage
  of resources especially with regard to large sparse matrices.
  The package can be accessed from an application through
  a straightforward interface defined in the form of procedure calls.
<LI>
  Besides the obligatory Jacobi, successive over-relaxation, Chebyshev, and
  conjugate gradient solvers,
  <tt> LASPack</tt>
  contains selected state-of-the-art algorithms
  which are commonly used for large sparse systems:
  <UL><LI>
    CG-like methods for non-symmetric systems: CGN, GMRES, BiCG, QMR, CGS, and
    BiCGStab,
  <LI>
    multilevel methods such as the multigrid and conjugate gradient methods
    preconditioned by multigrid and BPX preconditioners.
  </UL>
  All the above solvers are applicable not only to the positive definite or
  non-symmetric matrices,
  but are also adopted for singular systems
  (e.g. arising from discretization of Neumann boundary value problems).
<LI>
  The implementation is based on an object-oriented approach  
  (although it is programmed in C).
  Vectors and matrices are defined as new data types in connection with
  the corresponding supporting routines.
  The basic operations are implemented in such a way
  that they allow the programming of linear algebra algorithms
  in a natural way.
<LI>
  <tt> LASPack</tt>
  is extensible in a simple manner. 
  An access to the internal representation of vectors and matrices
  is not necessary and is avoided,
  as required of the object-oriented programming.
  This allows an improvement of algorithms or a modification
  of data structures with no adjustment of application programs
  using the package.
<LI>
  <tt> LASPack</tt>
  is written in ANSI C and is thus largely portable.
</UL><BR> <HR>
<P><ADDRESS>
Tomas Skalicky (skalicky@msmfs1.mw.tu-dresden.de)
</ADDRESS>
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